I'm 19 now. But 2.5 years ago, I was the same throughout high school. I never even took my unifrom jumper off in the heat... Even in class. I was a totally different person back then, and I wish I could go back in time and tell myself to stop being a weird little shit and just do whatever I want, without worrying about what people think. I was a total reclusive shy kid in high school, so it's been a long hard journey since then.

Things start to change for me when I got to College. I began to dress a lot better. Skinny jeans, larger longline tshirts. Long sleeve shirts etc. You will feel a lot better about yourself as I did, and people will definitely take notice of you since you're going through a change. But as long as you man it out, confidently without giving a fuck; People will pick up on that and their perception of you will probably be different. Even strangers who you only ever see around school everyday.

I'm from England, so I don't know what type of person you are socially. I understand that America has a broken social scene with cliques etc. But that said, I'd suggest not giving a fuck about what people say to how you dress. Especially if they try to make you feel bad for it. Even your friends. That would boil down to jealously of you bettering yourself. If you are comfortable with it, I strongly suggest that you adopt a style that will tailor to your body.

Coincidentally to this post, I made the decision today that I will start lifting this summer break. I've always had a problem with how much I can eat before feeling sickly. However, that recently hasn't been an issue since I started vaporizing marijuana(not smoking) at Uni 6 months ago. Hopefully, my stomach will get used to the food load after a bit so I wont have to get high to eat for much longer as I put mass on and stretch my stomach. I know for sure that I will get laughed at in the gym for how skinny I am, but I've already made the decision to not care and keep the long term goals in mind. I'm not suggesting that you start doing marijuana at all. I saw that you mentioned about being against drugs. So there are other ways to go about it, such as simply forcing yourself to eat big meals. However, since I did my research on the substance, I have found it to be a comfortable solution for my problem, even though I started smoking for fun.

I apologize for the length, and how much I talk about myself. But I figured that if I talked about my own similar experiences, it may help you figure a few things out. But if you're totally for change, then I'd consider looking at /r/MaleFashionAdvice and /r/Streetwear for inspiration.

Best wishes, and good luck mate.